How can I get a regex to check that a string only contains alpha characters [a-z] or [A-Z]?

Question

I\'m trying to create a regex to verify that a given string only has alpha characters a-z or A-Z. The string can be up to 25 letters long. (I\'m not sure if regex can check

Answer 1

/// 

/// Checks if string contains only letters a-z and A-Z and should not be more than 25 characters in length
/// 
/// String to be matched
/// True if matches, false otherwise
public static bool IsValidString(string value)
{
    string pattern = @"^[a-zA-Z]{1,25}$";
    return Regex.IsMatch(value, pattern);
}